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add vIOMMU documentation

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Signed-off-by: Markus Frank <m.frank@proxmox.com>
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Markus Frank 2024-04-11 12:48:21 +02:00 committed by Thomas Lamprecht
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50
qm-pci-passthrough.adoc
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@ -499,6 +499,56 @@ properly used with HA and hardware changes are detected and non root users
can configure them. See xref:resource_mapping[Resource Mapping]
for details on that.
[[qm_pci_viommu]]
vIOMMU (emulated IOMMU)
~~~~~~~~~~~~~~~~~~~~~~~
vIOMMU is the emulation of a hardware IOMMU within a virtual machine, providing
improved memory access control and security for virtualized I/O devices. Using
the vIOMMU option also allows you to pass through PCI devices to level-2 VMs in
level-1 VMs via https://pve.proxmox.com/wiki/Nested_Virtualization[Nested Virtualization].
There are currently two vIOMMU implementations available: Intel and VirtIO.
Host requirement:
* Add `intel_iommu=on` or `amd_iommu=on` depending on your CPU to your kernel
command line.
Intel vIOMMU
^^^^^^^^^^^^
Intel vIOMMU specific VM requirements:
* Whether you are using an Intel or AMD CPU on your host, it is important to set
`intel_iommu=on` in the VMs kernel parameters.
* To use Intel vIOMMU you need to set *q35* as the machine type.
If all requirements are met, you can add `viommu=intel` to the machine parameter
in the configuration of the VM that should be able to pass through PCI devices.
----
# qm set VMID -machine q35,viommu=intel
----
https://wiki.qemu.org/Features/VT-d[QEMU documentation for VT-d]
VirtIO vIOMMU
^^^^^^^^^^^^^
This vIOMMU implementation is more recent and does not have as many limitations
as Intel vIOMMU but is currently less used in production and less documentated.
With VirtIO vIOMMU there is *no* need to set any kernel parameters. It is also
*not* necessary to use q35 as the machine type, but it is advisable if you want
to use PCIe.
----
# qm set VMID -machine q35,viommu=virtio
----
https://web.archive.org/web/20230804075844/https://michael2012z.medium.com/virtio-iommu-789369049443[Blog-Post by Michael Zhao explaining virtio-iommu]
ifdef::wiki[]
See Also

1
qm.adoc
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@ -152,6 +152,7 @@ https://en.wikipedia.org/wiki/Intel_440FX[Intel 440FX] or the
https://ark.intel.com/content/www/us/en/ark/products/31918/intel-82q35-graphics-and-memory-controller.html[Q35]
chipset, which also provides a virtual PCIe bus, and thus may be
desired if you want to pass through PCIe hardware.
Additionally, you can select a xref:qm_pci_viommu[vIOMMU] implementation.
Machine Version
+++++++++++++++